Apparatus for making cross fin coils



Oct. 28, 1952 s. PRZYBOROWSKI I APPARATUS FOR MAKING CROSS FIN COILS 8 Sheets-Sheet 1 Filed April 23, 194'? INVENTOR.

borowskj Sfanislaw P1 7 1952 s. PRZYBOROWSKI 2,615,237

APPARATUS FOR MAKING CROSS FIN COILS Filed April 23, 1947 8 Sheets-Sheet 2 INVENTOR. co Sfamslaus Pr zyborowslcz.

ATTORN v Oct. 28, 1952 s. PRZYBOROWSKI 2,615,237

APPARATUS FOR MAKING CROSS FIN COILS Filed April 23, 1947 8 SheetsSheet 3 f 3= $3 .4 f) m w m A v JfamlslauqPrgyborowski ATTORNEY S. PRZYBOROWSKI APPARATUS FOR MAKING CROSS FIN COILS Oct. 28, 1952 8 Sheets-Sheet 4 Filed April 23, 1947 INVENTOR. .S'iamslaus Prp borowskz, BY /8 ATT Oct. 28, 1952 s. PRZYBOROWSKI 2,615,237

APPARATUS FOR MAKING CROSS FIN COILS Filed April 25, 1947 8 Sheets-Sheet 5 IN V EN TOR.

Sfapzlylaus Pczyborawaki,

A TTOR/VEY 8 Sheets-Sheet 6 w m m m ATTORNEY Oct. 28, 1952 s. PRZYBOROWSK] APPARATUS FOR MAKING CROSS FIN COILS Filed April 23, 1947 L M w r 0 0 y f P w M H h. J

BY W

Oct. 28, 1952 s. PRZYBOROWSKI 2,615,237

APPARATUS FOR MAKING CROSS FIN COILS Filed April 23, 1947 8 Sheets-Sheet '7 q Q Lg INVENTOR. J/a/ysluus Prjyboroa/Jkz,

ATTORN 1952 s. PRZYBOROWSKI APPARATUS FOR MAKING CROSS FIN 0011.5

8 Sheets-Sheet 8 Filed April 23, 1947 INVENTOR.

Siam la P1"; @f

ATTORNEY v Patented Oct. 28, 1952 UNITED STATES PATENT OFFICE APPARATUS FOR MAKING CROSS FIN COILS Stanislaus Przyborowski, Kenmore, N. Y., as-

signor to Fedders-Quigan Corporation, Buffalo, N. -Y., a corporation of New York Application April 23, 1947, Serial No. 743,385

" 3 Claims.

7 1 Thisinvention relates to apparatus for making cross fin coils, or coils useful for heat exchange purposes wherein a plurality of parallel tubes are traversed by a pluralityof metallic fins. The invention has especial utility in the fabrication of such structures wherein the stretchesof tubing are provided with integral return bends connect ing adjacent lengths, and the fins themselves are substantially continuous transversely of the tubes.

In my prior Patents Nos. 2,181,107 and 2,181,108 of November 21, 1939, I have disclosed a method and apparatus for fabricatin coils in which the tube is continuous by bending a straight length in serpentine fashion, so that separately formed return bends are eliminated, and wherein the fins,

, interconnecting both of them.

extending transversely of all of the tube stretches,

are also substantially continuous This result,

which provides a heat exchange coil free from" potential leaks and of high thermal efficiency, is obtained by nesting'the fins in properly spaced relation,'and weakening portions of them, as by punching and slitting, so that the preformed tube can be moved through the fin assembly, the return bends displacing the metalof the fins between the adjacent straight lengths. Thereafter, by means of dies contained inthe apparatus, the displaced portions of fin stock are-pushed back to their original positions in the plane of each fin, and into tight engagement with the tubes.

For the specific embodimentof the apparatus shown in thesepatents, I proposed that the fins be slit along a line joining the centers of pairs of adjacent tube apertures, and that the restoration of the pairs of fiaps-formed by the transfixing of the fins by the coil-should be effected by movement of pairs of die elements from each side of the assembly toward the line of centers. Such equipment has been employed successfully tomanufacture substantial numbers of heat exchange coils, such as those suitable as condensers for air cooled refrigerating machines. Where a multiple pass coil has been desired, two or more single pass coils, as made according to my prior inventions, have been assembled 'on a common frame, and the necessary connections made in the usual manner. 1

According to the present invention, improved apparatus is provided, by means of which a double pass coil, or one having two rows of straight tubing lengths which may be connected by integral return bends, may be formed with continuous cross fins in one operation. This new result is obtained by slitting or otherwise weakening the fin stock along lines of tangency to the tube apertures, rather than along a line of centers. The

single flaps for each row of tubing, formed b the transfixing operation, are thereafter restored into the plane of the fin by die elements which operate from each side of the assembly. However, in lieu of employing cooperative pairs of closing dies, for each displaced fiap, as in the specific embodiment of my prior patents, only one die'element is employed. It is therefore now possible to close the flaps from each side without interference, and thus produce a coil having two tube passes, and continuous or integral fin stock 1 The same apparatus is, of course, also applicable to the fabrication of single pass coils. Novel improvements over my original inventions include a new form of closing die element by means of which the displaced fin stock is wrapped around the adjacent tubes; mechanical means incorporated in the machine to eject or strip the coil from the die nest after its formation; and various improvements in the machine organization which will appear as this description proceeds. These facilitate the manufacture of heat exchange devices of this nature. They moreover enable the fabrication of coils having a'closer fin spacing, and therefore greater heat transference per unit of area, than was considered originally attainable.

In the following description of a typical embodiment of the improved machine, reference will be made to the appended drawings, wherein:

Fig. 1 is a front elevation of the machine as it appears at the completion of the fin and tube assembling operation;

Fig. 2 is a top plan, on an enlarged scale, with the upper portion of the die and cover removed;

Fig. 3 is a section taken substantially along the line 3-3 of Fig. 2, on a further enlarged scale, with the upper die assembly in position;

Figs. 4 and 5 are sections taken substantially on the line 4-4 of Fig. 1, to the scale of Fig. 3, and respectively showing the relative positions of the parts before and after the operation of the fin stock restoring dies;

Fig. 6 is a perspective of a portion of the die nest assembly;

Fig. 7 is a perspective of the end of a die finger;

Fig. 8 is a perspective of a. two-pass heat exchange coil made by the present apparatus;

Fig. 9 is a side view of a two-pass coil combined'with a single pass coil to form a threepass unit;

3 illustrating the action attendin the movement of the tubes relative to the fins;

Fig. 11 is a view similar to Fig. 10, showing the effect of actuating the closing or fin restoring dies; and

Figs. 12 to 15 inclusive are enlarged fragwhich is mounted a combined fin supporting and die structure 42, a tube supporting and impelling structure 43, and a die actuating structure 44. Additionally, the present machine includes a coil ejecting or stripping unit, generally indicated by the reference numeral 45.

The machine frame 4| comprises uprightsup- I porting legs 50-for a base plate 5| disposed at the left hand side, and from-which extend upwardly spaced end walls 52 and front and back side walls 53, thereby to provide a generally rectangular re ceptacle or holder 54 for a portion of the die and nest member '42. An inverted upper similar receptacle or holder 55is mounted above the holdof differentiation. Each pass is formedof a number of parallel tube lengths or stretches 24 and 25 respectively, and these are alternately connected in series at their Opposite ends by return bends 26 and 21, except for free terminal ends 28 and 29. Specifically, the return bends and stretches are integral with each other, and each pass is conveniently made by bending a continuous length of tubing intoserpentine form. In order to position continuous finson continuous tubes, it is necessary to cut away the fin stock so that the fin may pass over the return bends. If actually severed from the fin, the loss of stock would interrupt the continuity, lower the heat transfer capacity, and very frequently result in loose contact between fins and tubes.

It will be seen the the figure that continuity has been preserved, and this 'is effected by slitting the fin stock along lines which are approximately tangent to pairs of adjacent tube stretch apertures, as indicated by the numerals 3| and 32. This is also illustrated in Fig. 6, which fragmentarily shows a fin 2| in relation to the die and supporting elements. Such slits connect pairs of apertures 33, so that, when a tube pass is moved longitudinally of an assembly of fins, and toward the left as viewed in Fig. '8, the leading return bends displace the fin stock to a position away from the plane of the fin, and toward its upper and IOWer edges. Thereafter the voids between the connected tubes are filled by forcing the displaced stock back to substantially its initial position, thus providing a substantially continuous fin surface tightly engaging all of the tubes.

As in the case of my earlier machine, the prodnot so made may be used with or without subsequent' soldering of the joints.

Referring to Fig. 9, there is shown a portion of a fin an tube assembly as just described, together i with a single row or single pass unit having tubes 34 and fins 35, which :is framed therewith by means of heavy end plates 36. The fins 2| and 35 are discontinuous, being spaced by a gap 31 which reduces heat transference. This figure therefore illustrates both the prior art-practice of assembling a number of single row coils to make a multiple row unit, and also the present improvement whereby continuity is preserved for a multiple row unit.

In common with the machine of my prior invention, the improved machine operates by the method or procedure of supporting a plurality of fins in a nest or other suitable fixture, then moving the fin assembly relative to and lengthwise of the tube or tubes to transfix the fins, and thereafter inserting die members in the spaces between the displaced metal to its initial position. To this Y end, the present machine, as shown in Figs. 1 to the fins and the connected tube lengths to restore er 54, and it comprises a top 56, side walls 57, and end walls 58. The'upper holder 55 is removably mounted with respect to the lower holder 54, by means of hinge lugs 59 and BI, secured to the respective holders, and which receive ahinge pin 62. The upper holder and its contents may therefore. be moved away from the lower holder in order to insert fins in the machine. This pivotal "action is facilitated by means of a counterweight 63 secured to the upper holder 55. The front sides of the holders are providedwith complementary latches 64 and detents 65 to hold the receptacles together .orin superimposed rela-- tion. during the .coil forming operations, and the latches 64 may be operated simultaneously through -a.handlle 66 connected to a common latch pin rod 61, available from the front of the machine. 7

The base plate 5| is formed with .a' centrally disposed boss 68 provided with a bore t receive a vertically movable ram shaft H The upper end of theshaft 1|,is formed with a reduced section 12, upon which is mounted a platen 73, secured I to the shaft by a transverse pin 14. As best shown in Figs. 4 and 5, the edges of the platen 13 are adapted to slide freely over the adjacentsurfaoes of the side walls-53, so that the platen, and the members mounted thereon, are guided and maintained in correct alignment during their movement by the shaft H. Up and down movement of the platen T3 is eifected by the die actuating structure 44, which is conveniently mounted beneath the base plate 5 I.

The platen or die actuating structure includes a bifurcated bracket 16 bolted underneath the plate 5| 0f the main frame, to provide a support for a guide bearing I! for the lower end of the ram shaft H. The shaft H is longitudinally slotted intermediate its ends, as indicated by the referencenumeral 78, to receive the forward end of a horizontally reciprocable cam plate 79, which is guided in its movement by pairs of rollers -8l rotatably mounted between the legs of the bracket 16. The shaft opening 18 is provided with a cam roller 82 mounted on an axle disposed transversehr of the shaft H and cam plate i9, and this roller is positioned in a cam slot 83 formed in the plate 19. Asshown in Fig. 1, this slot is-so formed that as the plate 19 moves to the left, the shaft II is elevated, and as .the plate moves to the right, the shaft and attached platen 13 are lowered.

A depending arm 851formed on thecam plate 19 is provided with an adjustable set screw 86 adapted to abut a stop pad 8'! on the bearing boss I'Lso that the motion of the plate ES to the left, and the upward displacement of theplaten 13, maybe accurately gauged and limited to the requirements .of the particular coil assembly undergoing fabrication.

The operating motor for the cam plate 19 here- I05, and I06 are formed in takes the form of a pneumatic cylinder 9I se-i cured to the right hand side ofthe'bracket 15', and whose piston rod 92 is directly connected to the cam plate. Operation of the motor is effected by a supply of compressed air flowing from a supply line. 93 through a distributor 94 into a control valve 95, which may be set in a nuetral position, or to direct the air to either side of the motor piston through the lines 96 and 91. Upon movement of the valve operating handle 98 in one direction, as, for example, down, the pressure air fiows from the line 93 through the line 96, thereby shifting the cam plate to the left. Movement of the handle 98 upwardly reverses'the action, while shifting the handle to an intermediate. position disconnects the air from the cylinder v9|.

The combined fin supporting and tongue or flap restoring die structure 42, comprises sets oi platesfor the tube passes 23 and .22, respectively mounted in the holders 54 and 55. The lower set I (see Figs. 3, 4 and 6) includes a mounting plate I02 connected to the platen 13 by means of retaining screws I03. Relatively heavy end plates I04 at each end of the mounting plate I02 receive between them comparatively narrow die plates I05, which are'spaced by means of rectangular spacer plates I06. The end plates, die plates, and spacers are secured to each other by longitudinally extending through bolts I01, and this assembly is mounted on the plate I02 by means of machine screws I08 entering taps formed in the end plates I04. The die plates I05 are slightlythinnerthan the intended spacing of the fins 2 I, and the spacer plates I06 areslightly thicker than 'the fin stock and are'of lessvertical height than the die plates, so that the assemblyprovides a plurality of narrow pockets in each of which a fin may be supported on edge. Fins of various widths may be supported in the pockets by means of beams I09, in a manner which will be described more fully hereinafter.

Each die plate I05 is formed with a plurality of upstanding fingers I II, so spaced as to receive between adjacent fingers theadjacent stretches of tubing 25, and to engage, along their edges, flanges formed around the apertures 33 of the fins 2|. The fingers are provided with beveled top ends I I2, to facilitate insertion of fins between adjacent die plates I05. Fins placed in the pockets between the die plates are, therefore supported by the fingers against endwise movement, and significant displacement lengthwise of. the die set.

The edges of the plates I05, between the fingers I I I, are formed as die elements II3, the detailed formation of which is also shown in Fig. 7. Each such element, which is utilized to restore the fin stock displaced by a return bend 21, includes a ganerally V-shaped tip II4 provided with laterally disposed recessed portions II5'on one face which extend from the apex to the base of the tip. These surfaces are rounded or relieved of sharp corners, in order to avoid possible damage to the fin stock during the The tip portion H4 merges at its base on each side into arcuate grooves I I6 which in turn blend into the fingers I I I at each side, to provide crimping die sections to press the fin stock firmly against the adjacent tube. In order to accommodate relative movement-between the die set IOI and the supporting beams I09, the plates I04, with aligned slots I ll of sufiicient width and depth to avoid any interference.

The upper die set .I2I similarly' is formed of restoring operation.

by the upper tube pass 22.

the two assemblies are moved vertically toward each other. 1 The areas of the die plates I24, between the slots I28, constitute die fingers I29 of the same general character as the fingers H3, and which are intended to operate on the fin stock displaced Inasmuch as the structure and formation of such fingers has already been described, repetition is believed to be. unnecessary. 1

By inspection of Figs. 3', 4, and 5, it'will be seen that when the fins 2I are placed in the pockets between the lower supporting fingers I1 I, and the upper holder 55 is brought down over the lower holder 54, the die fingers I13 and I29 are, positioned in slightly spaced relation to the pairs of tube apertures 33 and their connecting slits 32 and 3I. When the platen I3 is elevated, the lower die set moves upwardly, to lift the fin assembly bodily, during which time the-die fingers H3 and I29 also move over the fin surfaces toward each other, and into the spaces between the pairs of apertures. When the platen is lowered, as shown in Fig. 4, the open regions between hold ing fingers III and the superimposed die fingers provide passageways for the return bends of the tubes and their contiguous straight stretches. When the platen is raised (Fig. 5), the mutual approach of the die fingers between such straight stretches forces any displaced fin stock back to its initial position. I

It will be noted thatthis basic'action' iszthe same as that in my earlier machine, but in'partial contradistinction thereto, the upper die assemblyis fixed with respect to the machine frame; and only one die finger is required to restore any given piece of displaced fin stock. When it is desired to use the machine to make a single pass coil, the upper die assembly I2I may be removed and replaced by a suitable stop piece, and the desired adjustment of the lower fingers II3 relative to the fin apertures effected by proper setting of the supporting beams I09.

The tube impellin-g unit 43, as best shown in Figs. 1, 2, and 3, includes an angle plate I3I centrallylocated with respect to and secured to the right side of the machine frame 4|. An air cylinder I33 is secured to a vertical leg I32 at the right hand extremity of the plate I3l with the axis of its piston rod I34 and piston I35 horizontally disposed and directed toward the holder and die assembly 42. The outer end of the piston rod I34 is connected to a crosshead. I36, which is, supported and guided for horizontal movement in a way I31 formed on the angle plate I3I. The face of the crosshead I36 is provided with a tube pushing block I38, which is formed with two vertically spaced rows of sockets I39, adapted to receive and supportthe trailing return bends 26 and 21 and the terminal ends 28 and 29.

In order to support the tube passes 22 and'23 durin the initial part of the transfixing operation, those portions of the right hand end plate I04 of the lower die assembly I0l corresponding.

to the diefingers H3 are formed with fiat upper surfacesin lieu of full tips I I4. The advancing or left hand return bends'may' therefore be laid on such flat surfaces, between the fingers I I I, thereby to support the tube pass- 23', through the return bends, at each end. The upper tube pass 22 is supported between the related socketsdw in the pusher block I38, and a removablecross bar I4'I', which is temporarily positioned on the lower pass 23 to provide proper supportand spacing. As shown in Fig. 3, this bar abuts the end pieces of the die assembly-the tubes simply sliding over it as they move to the left. The bar 1 It! may beremoved after the'tube impelling operation is completed. The advancing motion of the crosshead I31 and tubing may be determined and limited by an adjustable set screw I42 adapted to abut the upper holder wall 58.

Operation of the piston rod I34 is effected in a manner similar to that described for the motor for the platen 13. A control valve I44, similar to the valve 95, directs air from the'line 93 to opposite sides of the piston I35, through the lines I45 and I46, or else shuts off the air supply so that the piston does not move. After the tubing is positioned, as shown in the dot and dash lines of Fig. '2, it is advanced through the fins 2| contained in the holder 42, until the stop screw I42 strikes its abutment to prevent further motion. The tubing is then in the full line position shown in Figs. 2 and 3, withthe advancin return bends projecting beyond-theleft hand end plates I04 and 122, was to clear the die fingers. The valve I 44 is then reversed to'withdraw the crosshead 1 3s and holder I39, and thereafter the valve 35 is manipulated'to causethe die fingers to restore thefiaps of fin stock which have been bent outwardly by the action of the impinging advancing return bends. v

In order to facilitate the removal of the fin,

and tube assembly from the machine, there is provided the above referred to stripper mechanism 45. This mechanism comprises an elevator and supporting structure for the fin supporting beams I69, so that, upon upward movement of the beams with respect to the lower die set IQI, theassembled coil is ejected from the dies where it may be be conveniently reached and removed.

A pair of pneumatic cylinders I5I are bolted to the under surface of the base plate 5!, adjacent the end walls 52, and the base is drilled so that I the cylinder piston rods I52 may move vertically with respect to the base. Each piston carries a transversely disposed bar "I53 provided with a guide and retaining pm I 54 vertically movable in a slot I55 formed in the end wall. The top surfaces of the bars I53 receive a pair of plates I56 and I51 formed with a dovetail-like notch (see Figs. 3 and 6) in which is locked the complemen tarily formed ends of the beams I09. Screws I58 retain'the plates andbeams in position. ,Adjustable stop screws I 6| tapped into bosses I62 at the corners of the'base plate 5|, provide lower limit supports for the bars I53, so that the fin supporting beams I89 may be positioned in correct initial relationship with respect to the dies,

After the diemechanism 42 has been actuated to restore displaced fin metal,.the platen 13 is retracted to withdraw the die fingers H3 and I from the fins, and to lower the coil assembly onto the beams ID!) from which it was raised bythe preceding motion. The upper holder 55is then swung away from its ,operative superimposed position, by releasing the latches 6.4. If,desired;

the motion of the upper holder may be utilized fianging the openings 8 to actuate asuitable valve (not shown) similar to the valves and I44, to admit air to the lower portion of the cylinders I 5| orsuch admission maybe effected manually. In either event, the upward motion of the pistons I52 causes a like upward motion of the beams I 09, and, as the lower die'assembly IIH is now stationary, the beams lift the coil assembly so as to carry the fins and tubes up along the holding fingers III, and place the whim a position where the workman may easily grasp and remove it. The machine is then ready for another'charge of fins and tubes to fabricate another coil.

The progressive action of forming, connecting, and restoring the fin stock is more fully illustrated in the enlarged views, Figs. 10 to 15 inclusive. Referring first to Fig. 12, the fin stock is fed to a suitable. punch press or like tool, to

' provide pairs of openings I1I, indicated by the dot and dash lines n the figure. Each such opening is formed with small notches I12 and H3, facing toward the adjacent opening, and located from each other circumferentially a distance less than The stock. is then advanced to fianging dies, which strike out the metal around the openings IN to form flanges I'M pro jecting at substantially right angles from the plane of the fin 2i These flanges are interrupted by the notches H2 and I13. The fin stock is also slit along a line parallel to the line of centers between the apertures 33, which are formed by I 1 I, and the line of slitting joins the two inner notches I13. Inasmuch as these notches are only slightly displaced from the inner trace of the apertures, the slits M or 32 tially the same as the outside diameter of the tube which is to be placed through it.

. It'will be seen that if the weakened portion of the fin, defined by the area'between the apertures 33 and the notches I12 and 113, is impacted, as from in back of the plane of the paper, such portion will be-forced outwardly from the fin surface, and will tend to bend along the dotted line I15 in Fig. 12, which joins the outer notches I12. Such action, as shown in Fig. 13, may be obtained by using the return bend portion of the tubing as the impacting tool, to form an outstanding flap or tongue I16.

After the fins 2| have been formed and cut to size, they are positioned, as previously explained, in the pockets between the lowerdie plates I05, being retained in position by the holding fingers III. As shown in Fig. 10, the flanges I14 are then disposed under the relatively movable die elements H3 and I29 on the lower and upper plates I I35 and I24. In this figure, the flanges I14 are shown as being of less length than the actualspacing between the fins, but it should be understood that a closer spacing may be employed if desired.

.the tubes 22 and 23 are now moved from the right'to the left, as viewed in Fig. 10, the return bends 26 and 21 progressively strike the weakened portions of the fins, forcing out the flaps I16, which may successively underlap each other, depending on the tube diameter and fin spacing. Inasmuch as it has been proposed to notch the flanges I14 at circular spacingsof less than 180, it is also advantageous to flatten the advancing return bends slightly, as indicated by the numeral IT! in Fig. 10. The tubes may then advance through the fins with tight engagement on the undisplaced flange portion of the apertures 33, and which constitutes an are somewhat greater than 180. The advancing tube bends finally take the position shown by the dot and dash lines of Fig. 10, at which time the transfixing operation is completed.

The tongues or flaps I16 now overlap the tips of the die elements H3 and I29, and are in a position to be restored to their initial positions by relative vertical movement. Referring again to Fig. 13, it will be seen that the fiap I16 is slightly wider than the minimum space between the tubes, although the flap must pass through this restricted gap in order to be fully restored. To eifect the action, the die tips H4 are therefore formed as V-shaped members, so that they engage the flaps at the central point between the outer notches H2, and also at some slight distance from the surface of the fin.

The resulting action is illustrated in Fig. 14. Upon initial impact, caused by the movement of the die tips towards each other, as previously explained, the central portion of the fiap is bowed downwardly, thereby decreasing the transverse overall width so that the outer flanged edges may pass around the adjacent portions of the tube stretches. Once the corners of the flaps have passed around the tube surfaces, the edges of the flaps tend to follow the now-diverging tube surfaces, and due to the continued application of pressure and the resilience of the metal, the flaps are replaced in the plane of the fin.

As the dies continue to move over the fin surfaces, as shown in Fig. 15, and also in Fig. 11, the plane continuous surfaces of the die tips, below the recesses I 15, act to force the flap metal substantially into the plane of the fin, as though one were ironing out a ruffled surface. At this time, the arcuate die portions H6 engage the outer portions of the flanges I14, forcing and crimping them tightly against the contacting surface of the tubes. Upon withdrawal of the restoring dies, there is no further displacement of the metal, thereby resulting in a substantially continuous cross fin engaging a series of continuous tubes.

While the invention has been primarily described with respect to its application in forming a multiple pass cross fin coil having continuous tubes and integral return bends intersected by continuous fins, it will be understood that it is not limited to fabricating such coils, but that it may be employed for making other fin and tube assemblies. It will also be appreciated that the numerous improvements herein described are subject to modifications and variations without departure from the principles of the invention. Accordingly, it is not intended that the invention be restricted to the specific embodiment described, but that it should be deemed to encompass all such equivalents, substitutions, and alterations as are within'the scope of the following claims.

I claim:

restoring apparatus comprising a first set of a plurality of spaced plates between which fins are adapted to be supported on edge, spaced upstanding holding fingers formed on said plates, the edges of the plates between the fingers being formed adjacent said fingers with substantially semicircular die portions merging into tip die portions projecting beyond said semicircular portions, the height of said tip die portions as measured from the base of the semicircular portions being greater than twice the radius of said semicircular portions, a second set of spaced plates formed with die fingers, means to hold said second set aligned with the first named set of plates with the plates lying in a series of common parallel planes, means to hold the sets of plates in spaced relation and to move them into closer proximity while in said planes, said second set of plates being formed with alternate die fingers and slots, said slots having a width and depth to receive the holding fingers of the first set of plates when said sets are moved into close proximity, the die fingers of the second set having a width slightly less than the spacing of the holding fingers of the first set, the edges of said last named fingers being formed with arcuate die portions merging into projecting tip portions also having a height greater than twice the radius of said arcuate portions.

2. A fin retaining and flap closing die nest comprising a plurality of spaced parallel die plates forming a nest assembly having length, width, and height, spaced outstanding die fingers formed on the plates and disposed across the width of the nest, each of said die fingers having a base and a tip portion, said tip portion having sides tapering outwardly toward the base portion and towards adjacent die fingers, the edges of said die plates adjacent the base portions of the tips being formed as arcuate di portions, the height of the die fingers from base to tip extremity being greater than twice the radius of the arcuate die portions.

3. A fin retaining and fiap closing die nest as set forth in claim 2, wherein the die fingers are formed with recessed regions at each side of the tip portion and a substantially plane area on the face of the finger at the base of the tip and its recessed portions.

STANISLAUS PRZYBOROWSKI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,057,244 Maynes Oct. 13, 1936 2,156,538 Maynes May 2, 1939 2,181,108 Przyborowski Nov. 21, 1939 2,305,610 Ernst Dec. 22, 1942 2,339,032 Schlenzig Jan. 11, 1944 2,414,549 Nowak Jan. 21, 1947 

